1. Scope of Invention
This invention relates generally to systems for coating objects by vacuum deposition, and more particularly to an improved anti-fouling or arc-resistant feedthru fitting for transferring necessary high voltage and current into a plasma-producing conductive rod in the vacuum deposition chamber.
2. Prior Art
Vacuum deposition of vaporized metal and plasma-energized protective coatings onto the exterior and interior surfaces of objects such as plastic components for automobile manufacturers which require a high degree of uniformity and finish quality are well known. One major manufacturer of such equipment is F. J. Stokes Corporation.
These prior art vacuum deposition systems typically include a medium to large sized vacuum chamber, a large moveable rack or carriage for holding and supporting a plurality of objects for coating within the chamber, means for conveniently moving the loaded object support carriage into and out of the chamber, an arrangement for producing vaporized metal for depositing a first metallic layer of vaporized metal onto the surface of the objects and a source of vaporized protective liquid such as a monomer which is applied atop the vaporized metal first deposited onto the surfaces of the objects within the vacuum chamber.
The use of a plasma created within the vacuum chamber in the vicinity of the metal coated objects is also typically utilized to energize the vaporized liquid monomer and to accelerate the liquid monomer within the vacuum chamber to facilitate a uniform protective coating applied to the objects.
However, the support and transfer of high voltage and current components of current systems into the elongated conductive rod which produces the plasma in the vacuum chamber required for metal deposition also become coated with the same vaporized deposition material. The previous U.S. Pat. Nos. 5,895,531 and 5,970,908 were directed to eliminating the degradation of the conductive rod during periods of downtime when the vacuum in the chamber is removed to atmospheric conditions for loading and unloading of objects for metal deposition.
The build-up of conductive vaporized deposition material can accumulate on the non-conductive outer support shields which both support the conductive rods and deliver the necessary high voltage current into the rods to the point where arcing occurs between the inner elongated conductive core of the thru fitting and the conductive sides of the chamber. This requires removal and manual cleaning of the deposited metal onto the ceramic non-conductive surfaces of the thru fitting before it may be placed back into service.
A separate removable cover for the feedthru electrodes is currently used to completely shield the electrode but this requires a separate shut-down of the system in order to remove those covers during normal operation of the plasma deposition of vaporized metal.
This invention is directed to an improved apparatus for initial ion cleaning, vapor metal deposition and protective coating of objects by vacuum deposition, the improvement including a high voltage, high current feedthru fitting with anti-fouling and arc-free characteristics. The apparatus includes a vacuum chamber for receiving the objects which are held on a movable rack or support. A metal such as aluminum is vaporized centrally in the chamber in a well known fashion after the chamber has been substantially evacuated of air molecules for uniform vapor deposition of the metal atop exposed surfaces of the objects. The improved feedthru fitting is connected through a wall of an elongated housing which is connected over an elongated opening formed through a chamber side wall. An elongated conductive preferably aluminum rod is disposed within the housing along the opening into the chamber interior generally coextensive with two apertured delivery tubes or members positioned within the housing. The conductive rod is electrically isolated from the housing and chamber and connected to a d.c. or a.c. high voltage power source as a cathode by one or more of the improved feedthru fittings to produce plasma during ion cleaning and when applying the protective monomer coating.
It is therefore an object of this invention to provide an improved apparatus for protectively coating vapor metalized coated objects within a vacuum chamber.
It is yet another object of this invention to provide a uniquely configured non-fouling arc-resistant high current high voltage feedthru fitting or electrode positioned within a side cavity through a hole in a wall area of the vacuum chamber for supporting the conductive plasma producing rod.